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The ceph-volume tool aims to be a single purpose command line tool to deploy
logical volumes as OSDs, trying to maintain a similar API to ceph-disk when
preparing, activating, and creating OSDs.

It deviates from ceph-disk by not interacting or relying on the udev rules
that come installed for Ceph. These rules allow automatic detection of
previously setup devices that are in turn fed into ceph-disk to activate
them.

By making use of LVM tags, the lvm sub-command is
able to store and later re-discover and query devices associated with OSDs so
that they can later activated. This includes support for lvm-based technologies
like dm-cache as well.

For ceph-volume, the use of dm-cache is transparent, there is no difference
for the tool, and it treats dm-cache like a plain logical volume.